Classical methods for separating analytes from water and other fluids use liquid/liquid extraction (LLE) procedures wherein the analyte is preferentially partitioned from an aqueous based liquid into an immiscible extraction liquid phase. Efficiency and selectivity of extraction of specific analytes by LLE is dependent on the partition coefficient of the analyte between the two liquids and is limited by the type of extraction liquid that can be used. Recently, solid phase extraction (SPE) procedures have been developed using solid particulate phases which can interact with the analyte by ion exchange, chelation, covalent bond formation, size exclusion, sorption, and other mechanisms to bind and remove the analyte from the fluid. SPE processes are described in Analytica Chimica Acta, 236, 157-164 (1990) and LC/GC, 9:5, 332-337 (1991). Application of mixed-mode SPE using copolymerized mixed-mode resins where C.sub.18 (octadecyl) and sulfonic acid functional groups are in closer proximity than on "blended" mixed mode resins is reported in J. Chrom. 629 (1993) 11-21.
The type of SPE particulate chosen to effect separation of specific analytes can be inorganic, inorganic with organic coatings, inorganic with covalently bonded organic functional groups, polymeric organic resins and derivatives thereof.
U.S. Pat. No. 4,895,662 describes a process for purification of aqueous effluent from bleaching of wood pulp using macroporous adsorbent resins having been post-crosslinked in the swollen state and functionalized with hydrophilic groups prior to contact with the waste effluent.
U.S. Pat. Nos. 5,104,545 and 5,135,656 describe a process for removing water soluble metal salts of organic acids from oil field water using nonionogenic macroreticular adsorption resins such as XAD-16.TM. from Rohm and Haas Co., Philadelphia, Pa.
U.S. Pat. Nos. 5,071,565 and 5,230,806 describe neutral functionalized resins which take up organics by adsorption rather than ion exchange and teach that the amount of functional group relative to the amount of poly(styrene divinylbenzene) is not critical. They teach that the functional group must be neutral since anionic or cationic resins may pick up undesirable materials that are present. Utility of these resins for SPE of phenols was reported by J. S. Fritz et al. in J. Chrom. 641 (1993) 57-61.
U.S. Pat. No. 5,114,591 describes ion exchange resins for reducing organic material content of paint booth waste water having functional groups that provide ion exchange activity and also adsorb neutral molecules in varying degrees.
U.S. Pat. No. 5,236,594 describes a process for removing specific toxicants containing at least one carboxylate group from aqueous petroleum waste streams using non-ionic macroreticular polymeric resins.
U.S. Pat. No. 4,537,683 describes anion exchange particles alone or anion exchange particles combined with cation exchange particles in the form of a floc. It is reported that the level of ion exchange functionality has only a limited effect on the particles' ability to remove trihalomethane precursors.
U.S. Pat. No. 5,279,742 describes solid phase extraction media and methods using sorptive particulate in particulate loaded PTFE matrix sheet configurations wherein disks of the same or different compositions can be stacked to achieve separations.
A major requirement for particulate useful for SPE is that it has sufficient sorptive capacity to retain the analyte of interest. The retention characteristics of a specific analyte by a sorptive particulate is expressed numerically as its "capacity factor (k')", see "Contemporary Practice of Chromatography", C. F. Poole and S. A. Schuette, Elsevier, New York, N.Y. (1984) pp 2-6.
J. J. Sun and J. S. Fritz in J. Chrom. 522 (1990) 95-105 describe chemical modifications of polymeric resins to increase analyte capacity factor (k') for high performance liquid chromatography applications.